测试代码及其输出如下: publicclassOptionalDemo{//methods from 2.1 to 2.5publicstaticvoidmain(String[] args){ optionalWithStream();// 输出:Get WANG ER with family name Wang!Personperson=newPerson();//fetchPersonFromSomewhereElse()System.out.println(newOptionalDemo().fromWhere(person));// 输出:f...
* Checks that the specified object reference is not {@code null}. This * method is designed primarily for doing parameter validation in methods * and constructors, as demonstrated below: * <blockquote> * public Foo(Bar bar) { * this.bar = Objects.requireNonNull(bar); * } * </blockquo...
5、do not have accessible constructors, but are instead instantiated through factory methods which make no committment as to the identity of returned instances; 6、are freely substitutable when equal, meaning that interchanging any two instances x and y that are equal according to equals() in an...
Java 8 Tutorial 接口的默认方法(Default Methods for Interfaces) Lambda表达式(Lambda expressions) 函数式接口(Functional Interfaces) 方法和构造函数引用(Method and Constructor References) Lamda 表达式作用域(Lambda Scopes) 访问局部变量 访问字段和静态变量 访问默认接口方法 内置函数式接口(Built-in Functional Inte...
java.lang.Object java.util.Optional<T> public final classOptional<T>extendsObject A container object which may or may not contain a non-null value. If a value is present,isPresent()will returntrueandget()will return the value. Additional methods that depend on the presence or absence of a...
In gender Option, value available. Copy 5. Optional orElse methods It returns the value if present in Optional Container. Otherwise returns given default value. OptionalOrElseExample.java packagecom.mkyong;importjava.util.Optional;publicclassOptionalOrElseExample{publicstaticvoidmain(String[] args){ ...
Methods injava.utilthat returnOptional Modifier and TypeMethod and Description static <T>Optional<T>Optional.empty() Returns an emptyOptionalinstance. Optional<T>Optional.filter(Predicate<? superT> predicate) If a value is present, and the value matches the given predicate, return anOptionaldescribi...
You can also use theisPresent()method to find out whether a value is present in anOptionalobject. In addition, there's aget()method that returns the value contained in theOptionalobject, if it is present. Otherwise, it throws aNoSuchElementException. The two methods can be combined, as fol...
Additional methods that depend on the presence or absence of a contained value are provided, such as #orElse(int) orElse() (returns a default value if no value is present) and #ifPresent(IntConsumer) ifPresent() (performs an action if a value is present). ...
Additional methods that depend on the presence or absence of a contained value are provided, such as#orElse(double) orElse()(returns a default value if no value is present) and#ifPresent(DoubleConsumer) ifPresent()(performs an action if a value is present). ...